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I cant use l'Hôpital's rule

  1. Nov 29, 2011 #1
    1. The problem statement, all variables and given/known data

    Hey guys.

    Can I please have some help with this limit over here

    http://imageshack.us/photo/my-images/839/targil.jpg/

    BTW

    I cant use l'Hôpital's rule.

    I'm trying to help someone how haven't learned how to Derivative yet.

    Thanks a lot.

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 29, 2011 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Re: Limit

    Multiply both the numerator and denominator with
    [tex](\sqrt{x^2+1}+1)(\sqrt{x^2+16}+4)[/tex] and simplify.

    ehild
     
  4. Nov 29, 2011 #3
    Re: Limit

    It will switch between the numerator and the denominator and will change the sign of the 1 and 4.

    How can that help?

    Thanks a lot.
     
  5. Nov 29, 2011 #4
    Re: Limit

    Ops, that's the solution.

    Thanks a lot.
     
  6. Nov 29, 2011 #5

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Re: Limit

    You are welcome. And remember the method, it is always useful when you have difference including square root(s)

    ehild
     
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